Devices that mix and spray pressurized fluids such as paints and resins have progressed in the art. Certain materials need to be mixed just before application, for example, a resin and a catalyst. If mixed before application, depending upon the time lag between the mixing and the application steps, the mixed resin and catalyst may settle, providing an uneven application, or even worse, may begin to harden.
Resins have numerous uses including forming and coating boat hulls, spas/hot tubs, bath tubs, sinks, etc. A resin such as polyester is typically mixed with a catalyst such as methyl-ethyl-ketone peroxide and applied to a surface. Catalysts allow the resin to cure, otherwise, the resin would remain fluid and sticky.
Early spraying systems emitted resin from one nozzle and catalyst from a second nozzle, in theory, mixing the resin and catalyst in air and after contact with the target surface. Such devices effectively spray the resin and catalyst, but uniform mixing of the resin and catalyst is important for proper application to various surfaces.
U.S. Pat. No. 2,878,063 to Stephen P. Kish is an example showing a spray gun in which the catalyst and resin are mixed in a stream of air emanating from a trigger gun. This is an example of an external mix gun. In an external mix gun, the resin and catalyst are atomized separately and directed toward each other. The resin and catalyst combine in the air before contacting the target. As discussed previously, this often results in an incomplete mixing of resin and catalyst. When the catalyst is atomized separately from the resin, much of the atomized catalyst disperses into the atmosphere and in the work environment where the application is taking place. This causes safety concerns for people breathing catalyst contaminated air leading to restricted use of external mix guns.
A gun in which the resin and catalyst are mixed internally is often used when solvent emissions are a problem, because internal mixing reduces the amount of atomized catalyst escaping into the atmosphere. Internal mix guns typically have three inputs: resin, catalyst, and air, all three under pressure. In the past, the resin and catalyst are typically mixed in the manifold. The mixture of resin and catalyst are then expelled from a gun through a nozzle along with pressurized air. The resin and catalyst are atomized by the pressurized air.
In some prior spraying devices, the resin and catalyst are introduced into a mixing area where they combine as they flow toward a spray tip or nozzle. A pressurized air stream helps mix the catalyst and resin and also helps expel the catalyst/resin mixture from the nozzle. In such designs, if there is an imbalance in the pressure of the resin and catalyst, the combined resin and catalyst will back up into the supply that has lower pressure, especially if a clog occurs. Furthermore, it is undesirable to introduce catalyst at the same high pressures of the resin since the catalyst is often less viscous and, at times, a serious health risk. It is also difficult to mix the catalyst and resin in the mixing area because, often, the relatively high viscosity catalyst often creates a tunnel through the resin within the mixing area instead of completely mixing with the resin.
What is needed is a system, method and apparatus that will mix two or more components with pressurized air and emit a mixed stream for spraying onto a surface.